Key fob trouble

[bennesspipers]

When i bought my w202 C220 only 1 of the ignition key fobs worked,on investigation there are parts missing inside,but it is the right metal key blade. Is it possible to 'train' another key fobs guts to work on my car,or does it mean spending £200 to have a spare key ?

 

[andy27168]

Hi,
You will have to buy new i,m afraid, as there is no way to reprogramme a used key.

 

[Dec]

Could you put up a close up picture of the front and back of the PCB, it is possible that something like the tactile switch is broken and could be repaired if a donor key was found, just a shot in the dark, it all depends what is missing.

Dec

 

[bennesspipers]

Hi Dec, what iv done is transferred my metal keyblade to another (complete) key fob, but i cant actually get the key fob completely opened up. Even though iv followed instructions in the owners book for when you change batts it doesnt work,of course i dont know if it did before i obtained it ! John

 

[Dec]

No need to open the battery compartment, it’s the joint (lenthwise) in the center that needs to be opened As you can see from the picture it will come apart, it’s a “snap together fit” you will need to lever it open with a knife, hopefully no one has previously super glued it together.

This is just a shot in the dark, otherwise there is no other solution other than what Andy above sayes.

Dec

 

[bennesspipers]

Thanx, bet it has been glued, iv already been rough with it,but, nothing ventured ! I'll try harder, nothing to lose.

 

[Dec]

If you didn’t get the key fob completely open how would you know that there are bits missing?
Could it be that there is only one battery in the fob, there should be 2 x 3v batteries inside.

Dec

 

[bennesspipers]

The green electronic bit that the batteries sit on was all missing,thanx very much for your brill pics on how to open,will have chance to try later,thanx again,much appreciated, John.

 

[Dec]

The green is the PCB board, the silver bit that the bottom of the battery sits on may have been pulled out, need to take it apart to see what damage there is.

Dec

 

[Dec]

By the way, in the picture in post #5 the batteries are the WRONG way around, the are the correct way around in post #7

Dec

 

[bennesspipers]

Dec,iv forced it open,blasted superglue,looks ok inside, put it together again, & its passed your camera test. But, pointed at interior mirror & clicked twice, as it says in handbook, nothing !

 

[Dec]

I believe it is as follows

Sit in car
Point fob at mirror
Press button twice in quick succession…(if twice doesn’t work , try once briefly instead)
Put key in ignition and turn to position 2… WITHIN 30 seconds, don’t start

Bear in mind, if the battery contact is a bit suspect , it may have worked ok for the camera but stopped working when you used it on the mirror.

Dec

 

[bennesspipers]

Just tried all that,& with door locked & unlocked, & tried pressing while its in ign, no joy im afraid, thanx anyway, john

 

[Dec]

Assuming the fob is unbroken, the only other possibilities is that the batteries aren’t up to the job or it’s the wrong key for that car, perhaps the last owner of the car OR the person who sold the car to you could answer that question.

Dec

 

[bennesspipers]

Batteries are brand new,as i said, fob is secondhand because correct fob had parts missing.can i ring you, be nice to have someone who knows something about the C class. My number 01205761044

 

[Dec]

Hi,
You will have to buy new i,m afraid, as there is no way to reprogramme a used key.

Andy, just to update this, John has a working keyfob and a spare keyfob, the spare key fob has the complete PCB board missing so he swapped over the blade on to another keyfob from a completely different car, the result is as you have said, and a new required.

Dec

 

[kml42]

Dec - Superb pics and advice! (especially that trick with the digital camera to detect the absence of IR transmission).
Having just got home with my new toy (95 SL 320) I was beginning to worry that the 'spare' fob was toast and looking at that nasty Merc bill for a new one. Your pics encouraged me to get the thing apart (something of a struggle!) and sure enough, the little button had come off the PCB (much as it looks like the one in the pics has). 2 minutes with a fine soldering iron and we're back in business! Result!
Sorry bennesspipers - sounds like your solution will be a tad more expensive :-(